It's not a bug -- it's a rendering choice made by the browser. As we
kneel before the altar of the "ha ha, you can't control what your
documents look like in HTML" philosophy, you, dear sinner (nay,
blasphemer), can but take solace in the fact that Mosaic is putting a
blank line at the start of all toplevel lists, including yours,
entirely on purpose. (Why? Primarily because we thought that looked
the best for most documents on the Web at the time, as I remember.)

What can you do about it? Probably nothing. Isn't that cheery news?
I think so. In fact, it has been a constant source of delight for me
over the past year to get to continually tell hordes (literally) of
people who want to -- strap yourselves in, here it comes -- control
what their documents look like in ways that would be trivial in TeX,
Microsoft Word, and every other common text processing environment:
"Sorry, you're screwed."